The invention relates to a bidirectional pressure supply system for controlling various consumers of pneumatic pressure or the like in a motor vehicle, such as door locking systems, air conditioner valve controls and the like.
A bidirectional pressure supply system of the generic type is known (German Pat. Specification 3,243,411). The electrically driven air pump described in that publication has (FIG. 1 of the German patent) a positive pressure connection and a negative pressure connection. From each connection a line leads to a pneumatically reversible 4/2-way directional control valve, which connects central-locking actuator elements as a complete group to positive pressure or negative pressure, depending on its switching position.
Connected into the Positive Pressure line between pump and pneumatic directional control valve --in series with the latter --is an electromagnetically switchable 3/2-way directional control valve for alternate connection of the central-locking actuating elements or of a pure positive pressure consumer (backrest air cushion) to the positive Pressure connection of the air pump. The positive Pressure line branch has a non-return valve, a Pressure control valve and a suPPly tank as well as a pressure-monitoring switch. The latter ensures maintenance of the required Pressure level in the supply tank when the ignition is switched on, by automatic triggering of the air-pump drive motor.
The limit-stopping of the latter takes place by means of an electric switch coupled to the pneumatic drive of the 4/2-way directional control valve or by means of the separately arranged pressure-monitoring switch.
In a further exemplary embodiment of the German patent (see its FIG. 2), in the same way, the negative pressure delivery of the air pump for the supply of pure negative pressure consumers (air conditioner systems --valve control) and the central-locking actuating elements, likewise a non-return valve, an expansion tank and a (negative) pressure-monitoring switch are provided.
Furthermore, German Published Unexamined Patent Application (DOS) 2,232,956 and U.S. Pat. No. 3,096,112 already disclose pressure generators which simultaneously generate negative Pressure and positive Pressure and --according to the German DOS --admit both tYPes of Pressure simultaneously to one consumer (break booster) for Power boosting or according to the U.S. patent - admit negative pressure to two consumers and positive pressure simultaneously to two other consumers. However, all the consumers in the U.S. patent are central-locking actuating elements which are always operated simultaneously and in the same direction.
With the arrangement reflected in the above-noted prior art, it is not possible to operate consumers demanding different pressure types (negative pressure and positive pressure) simultaneously but also independently of each other by means of the pressure generator. Rather, all pressure increasing and decreasing operations have to be successively executed. This requires a relatively complex control of the pump running time and of the pressure distribution valves, which depends on the overall equipment of the vehicle and is not especially flexible with regard to equipment modifications, for example during a production series. In addition, the "successive execution" may result in long pump running times. With the customary use of reversible bidirectional pressure pumps, repeated starting-up of the pump with alternate direction of rotation and deliverY may be necessary for each case.
An object of the invention is to design a bidirectional pressure supply system of the generic type in such a way that the control of the pressure generator and the pressure distribution to a wide variety of consumers is simplified in order to increase the flexibility of the system.
This object is achieved according to the invention by providing an arrangement with bidirectional control valves arranged parallel to each other and adopted to be electromagnetically switched independently of each other for selectively switching the respective consumer individual lines individually in groups between positions connected to the respective negative and positive pressure line system and position separated from both, and electrical triggering means for initiating operation of the pressure generation and admitting the respective supply of negative and positive pressure to the respective negative and positive pressure systems, wherein each of the negative and Positive pressure line systems contain a pressure-dependently responding limit stop switch for the pressure generator and a safety valve in the form of a blow-off valve in the positive pressure line system and an intake valve in the negative pressure line system, which safety valves only open after response of the associated limit stop switch in the same line system to protect the pressure generator against overloading when not consuming the respective pressure type (p.sub.u or p.sub.uml) if the pressure generator is in operation via the limit stop switch assigned to the other line system.
With the system of the preferred embodiments of the present invention, it consequently becomes possible, even with a large number of consumers of pneumatic pressure, growing all the time with increasing vehicle comfort requirements, to achieve a wide variety of objects with a unified bidirectional supply system. An example of simultaneous demand for positive pressure and negative pressure is the case where a motor vehicle with bidirectional pressure central locking (ZV) and pneumatic door sealing (PTD) is to be released. Positive pressure is admitted to the ZV, while the PTD requires negative pressure for detachment of the sealing hoses.
With the bidirectional pressure supply system according to the invention, the vehicle user is no longer obliged to wait for lengthy periods.
The pressure distribution can be controlled in the usual way by simple electrical triggering of the pressure generator on the one hand, whenever there is a requirement, and of a directional control valve or several control valves on the other hand, depending on the individual demand of the consumers, by means of electric switches assigned to the consumers.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.